Discharge lamp lighting circuit for increasing electric power fed in initial lighting of the lamp

Abstract

A discharge lamp lighting apparatus includes a voltage raising element for raising a DC input voltage, a pulse generator for varying the output voltage output by the voltage raising element is a pulse voltage having a given pulse width and outputting the pulse voltage, a bridge circuit for applying the pulse voltage to a discharge lamp, a voltage detecting element for detecting a voltage applied to the discharge lamp, a current detecting element for detecting a current running through the discharge lamp, an adder for adding a first amplification signal output by a first amplifier and a second amplification signal output by a second amplifier together, elements for delaying outputs from the amplifiers, and a pulse width modulator for controlling the pulse width of the pulse voltage.

What is claimed is: 
     
       1. In a discharge lamp lighting apparatus comprising voltage raising means for raising a DC input voltage, pulse generating means for varying an output voltage output by said voltage raising means to a pulse voltage having a given pulse width and outputting said pulse voltage, and a bridge circuit for applying said pulse voltage to a discharge lamp, said discharge lamp lighting apparatus further comprising: voltage detecting means for detecting a voltage applied to said discharge lamp;   current detecting means for detecting a current running through said discharge lamp;   first amplifying means for amplifying a voltage detection signal detected by said voltage detecting means;   second amplifying means for amplifying a current detection signal detected by said current detecting means;   first delaying means, connected in parallel to said first amplifying means, for delaying an output of said first amplifying means in order to increase electric power fed to said discharge lamp in initial lighting of said discharge lamp, said first delaying means comprising a resistance and a Zener diode;   second delaying means, connected in parallel to said second amplifying means, for delaying an output for said second amplifying means in order to increase electric power fed to said discharge lamp in initial lighting of said discharge lamp, said second delaying means comprising a resistance and a Zener diode;   adding means for adding a first amplification signal output by said first amplifying means and a second amplification signal output by said second amplifying means; and   pulse width modulating means for controlling the pulse width of said pulse voltage so that an addition signal output by said adding means becomes a predetermined value.   
     
     
       2. In a discharge lamp lighting apparatus comprising voltage raising means for raising a DC input voltage, pulse generating means for varying an output voltage output by said voltage raising means to a pulse voltage having a given pulse width and outputting said pulse voltage, and a bridge circuit for applying said pulse voltage to a discharge lamp, said discharge lamp lighting apparatus further comprising: voltage detecting means for detecting a voltage applied to said discharge lamp;   current detecting means for detecting a current running through said discharge lamp;   first amplifying means for amplifying a voltage detection signal detected by said voltage detecting means;   second amplifying means for amplifying a current detection signal detected by said current detecting means;   first delaying means, connected in parallel to said first amplifying means, for delaying an output of said first amplifying means in order to increase electric power fed to said discharge lamp in initial lighting of said discharge lamp, said first delaying means comprising a DC circuit of a resistance and an analogue switch;   second delaying means, connected in parallel to said second amplifying means, for delaying an output of said second amplifying means in order to increase electric power fed to said discharge lamp in initial lighting of said discharge lamp, said second delaying means comprising a DC circuit of a resistance and an analogue switch;   adding means for adding a first amplification signal output by said first amplifying means and a second amplification signal output by said second amplifying means; and   pulse width modulating means for controlling the pulse width of said pulse voltage so that an addition signal output by said adding means becomes a predetermined value;   the analogue switch of said first delaying means being turned on when the voltage detected by said voltage detecting means is more than a given voltage, the analogue switch of said second delaying means being turned on when the voltage detected by said voltage detecting means is less than a given voltage.   
     
     
       3. In a discharge lamp lighting apparatus comprising voltage raising means for raising a DC input voltage, pulse generating means for varying an output voltage output by said voltage raising means to a pulse voltage having a given pulse width and outputting said pulse voltage, and a bridge circuit for applying said pulse voltage to a discharge lamp, said discharge lamp lighting apparatus further comprising: voltage detecting means for detecting a voltage applied to said discharge lamp;   current detecting means for detecting a current running through said discharge lamp;   first attenuating means for attenuating an output of a voltage detection signal detected by said voltage detecting means in such a way as to enlarge an attenuation degree according to the increase of a voltage of said voltage detection signal, in order to increase electric power fed to said discharge lamp in initial lighting of said discharge lamp, said first attenuating means comprising a plurality of comparators;   second attenuating means for attenuating a current detection signal detected by said current detecting means in such a way as to enlarge an attenuation degree according to the increase of a voltage of said current detection signal, in order to increase electric power fed to said discharge lamp in initial lighting of said discharge lamp, said second attenuating means comprising a plurality of comparators;   adding means for adding a voltage attenuation signal output by said first attenuating means and a current attenuation signal output by said second attenuating means;   comparing means for comparing the value of an addition signal output by said adding means with a predetermined reference value and outputting a resultant comparison signal; and   pulse width modulating means for controlling the pulse width of said pulse voltage so that said comparison signal becomes zero.   
     
     
       4. In a discharge lamp lighting apparatus comprising voltage raising means for raising a DC input voltage, pulse generating means for varying an output voltage output by said voltage raising means to a pulse voltage having a given pulse width and outputting said pulse voltage, a bridge circuit for applying said pulse voltage to a discharge lamp, voltage detecting means for detecting a voltage applied to said discharge lamp, current detecting means for detecting a current running through said discharge lamp, first amplifying means for amplifying a voltage detection signal detected by said voltage detecting means, second amplifying means for amplifying a current detection signal detected by said current detecting means, adding means for adding a first amplification signal output by said first amplifying means and a second amplification signal output by said second amplifying means, and pulse width modulating means for controlling a pulse width of said pulse voltage so that an addition signal output by said adding means becomes a predetermined value, said discharge lamp lighting apparatus further comprising: first delaying means, connected in parallel to said first amplifying means, for delaying an output of said first amplifying means in order to increase electric power fed to said discharge lamp in initial lighting of said discharge lamp, said first delaying means comprising a resistance and a Zener diode; and   second delaying means, connected in parallel to said second amplifying means, for delaying an output of said second amplifying means in order to increase electric power fed to said discharge lamp in initial lighting of said discharge lamp, said second delaying means comprising a resistance and a Zener diode.   
     
     
       5. In a discharge lamp lighting apparatus comprising voltage raising means for raising a DC input voltage, pulse generating means for varying an output voltage output by said voltage raising means to a pulse voltage having a given pulse width and outputting said pulse voltage, a bridge circuit for applying said pulse voltage to a discharge lamp, voltage detecting means for detecting a voltage applied to said discharge lamp, current detecting means for detecting a current running through said discharge lamp, first amplifying means for amplifying a voltage detection signal detected by said voltage detecting means, second amplifying means for amplifying a current detection signal detected by said current detecting means, adding means for adding a first amplification signal output by said first amplifying means and a second amplification signal output by said second amplifying means, and pulse width modulating means for controlling a pulse width of said pulse voltage so that an addition signal output by said adding means becomes a predetermined value, said discharge lamp lighting apparatus further comprising: first delaying means, connected in parallel to said first amplifying means, for delaying an output of said first amplifying means in order to increase electric power fed to said discharge lamp in initial lighting of said discharge lamp, said first delaying means comprising a DC circuit of a resistance and an analogue switch; and   second delaying means, connected in parallel to said second amplifying means, for delaying an output of said second amplifying means in order to increase electric power fed to said discharge lamp in initial lighting of said discharge lamp, said second delaying means comprising a DC circuit of a resistance and an analogue switch;   the analogue switch of said first delaying means being turned on when the voltage detected by said voltage detecting means is more than a given voltage, the analogue switch of said second delaying means being turned on when the voltage detected by said voltage detecting means is less than a given voltage.   
     
     
       6. In a discharge lamp lighting apparatus comprising voltage raising means for raising a DC input voltage, pulse generating means for varying an output voltage output by said voltage raising means to a pulse voltage having a given pulse width and outputting said pulse voltage, a bridge circuit for applying said pulse voltage to a discharge lamp, voltage detecting means for detecting a voltage applied to said discharge lamp, current detecting means for detecting a current running through said discharge lamp, comparing means for outputting a comparison signal, and pulse width modulating means for controlling a pulse width of said pulse voltage so that said comparison signal becomes zero, said discharge lamp lighting apparatus further comprising: first attenuating means for attenuating an output of a voltage detection signal detected by said voltage detecting means in such a way as to enlarge an attenuation degree according to an increase of a voltage of said voltage detection signal, in order to increase electric power fed to said discharge lamp in initial lighting of said discharge lamp, said first attenuating means comprising a plurality of comparators;   second attenuating means for attenuating an output of a current detection signal detected by said current detecting means in such a way as to enlarge an attenuation degree according to an increase of a voltage of said current detection signal, in order to increase electric power fed to said discharge lamp in initial lighting of said discharge lamp, said second attenuating means comprising a plurality of comparators; and   adding means for adding a voltage attenuation signal output by said first attenuating means and a current attenuation signal output by said second attenuating means and outputting an addition signal to said comparing means;   said comparing means comparing a value of said addition signal with a predetermined reference value and outputting a resultant comparison signal.